Replacement sails - Hood''''s Vektran
I don''t think any of us can judge the condition of your sails from the above description.
If you can absolutely only buy one new sail, and if the old mainsail is likely to fail, it seems to me that you have to replace the mainsail first. It''s no fun to sail a boat with a new 130% jib and no mainsail.
If you are only doing coastal cruising (so that, if the sail fails, you aren''t far from shelter), and, if you could afford to buy a second sail if absolutely necessary, then I would buy the jib and hope the mainsail holds up until Santa brings me a new mainsail.
At the moment, I''m a retiree putting a big chunk of my income into my son''s college expenses, and when I needed new sails, I bought inexpensive Rolly Tasker dacron sails, and she''s as fast as she was when my old North sails were new. We''re crossing the finish line ahead of boats that have to give us lots of handicap time. I don''t expect the Rolly Taskers will hold up as long as the Norths, but they''ll last at least until my son graduates, and probably a good deal longer.
You have lots of options, but you have to decide what works for you, considering all your circumstances.